One ROCK is not like another

The mammalian rho kinases, ROCKI and ROCKII, control distinct cytoskeletal functions from distinct locations, report Yoneda et al. on page 443. ROCKI is required for formation of actin stress fibers and cell adhesion, whereas ROCKII is needed for phagocytosis.The ROCK proteins are major effectors of the Rho signaling pathway, controlling cell adhesion, motility, and other actin-based functions. In kinase overexpression assays, ROCKI and ROCKII appear redundant, but several experiments, including mouse knock-outs, hinted that the proteins have unique duties despite their structural similarity.

While studying a signaling pathway that links integrins and cell surface proteoglycans to adhesion, Yoneda et al. saw that ROCKI but not ROCKII activity increased during adhesion. To learn how the proteins differ functionally, the team knocked down each ROCK gene independently using siRNA sequences that left the other gene unchanged. Cells lacking...